Difference between Fluoride and Arsenic.
The major source of fluoride to man is drinking water. In most parts of India the fluoride content is about 0.5 mg/L. There are, however, some areas where fluoride content in drinking water may be as high as 3 — 12 mg/L. The recommended level of fluoride in drinking water accepted in India in 0.5 to 0.8 mg/L. High intake of fluoride causes humped back. Continuous consumption causes stiffness of bone joints, particularly spinal cord. It accumulates in bones causing outward bending of legs from knee-called Knock Knee Syndrome. Water rich in fluoride cause endemic fluorosis. It was first detected among cattle’s by the farmers of Andhra Pradesh in early 1930’s. Excess fluoride is removed by Nalgond techniques. It involves the addition of lime and alum in sequence followed by flocculation, sedimentation and filtration.
Arsenic is introduced into water via the dissolution of minerals and ores, from industrial effluent and from atmospheric deposition. A provisional guideline value for arsenic in drinking water of 0.01 mg/L. World’s worst affected areas due to Arsenic contamination is the Indo-Bangladesh region. WHO has alarmed Govt. of India to keep Arsenic related disease under immediate national surveillance, giving it a status similar to that of cancer. WHO prescribed limit to 0.01 mg/L.
At higher levels, As(III) compounds coagulates proteins, possibly by attacking S-bond retaining the secondary and tertiary structure of proteins. In the biological systems, Arsenic compounds complexes will co-enzymes resulting in coagulation of biological proteins and uncoupling at phosphorylated sites. The effect on human depends on the arsenic dosage. Thus
Mild Dose → nausea, fainting, salivation, vomiting, burning pain in stomach.
Higher Dose diarrhea, peripheral neuritis, hyperketosis, conjunctives. Chronic Dose — severe gastroenteritis, less of weight, skin lesions, black food disease.